biology Flashcards
Allele
Different versions of a gene; alleles are genes that occupy the same position on homologous chromosomes
Asexual Reproduction
Reproduction only involving one parent producing identical offspring
Bases
Adenine, Guanine, Cytosine, Thymine
Carrier
Has inherited a genetic trait or mutation, but who does not display the trait, but can pass it on to their offspring
Characteristic
(also known as a trait), an attribute of an individual e.g tall plant, brown hair, blue eyes
Chromosome
Strand of DNA which contains many genes; a normal human cell has 46 (23 pairs)
Complementary Base Pairing
Used to describe how the bases A always bond with T, and C with G
Continuous Variation
Variation that shows a range e.g skin colour / gradual changes e.g height and weight
Diploid
Cell with the full complement of chromosomes (46 in humans)
Discontinuous Variation
Variation that is ‘either/or’ e.g blood groups, ability to roll tongue or not
DNA
This is the chemical which carries genetic information in the nuclei of cells, made up of phosphate units, sugar units and 4 types of bases.
Dominant
This is the allele which will be ‘expressed’ in the phenotype if it is present as either a single gene or as two genes e.g B
Double Helix
Name given to the twisted ladder shape of the DNA
Fertilisation
Male sex cell (gamete) combines with a female sex cell (gamete) to form a zygote
Gamete
A sex cell i.e sperm or egg (ovum) in animals. Ovum and pollen in plants
Gene
Piece of DNA which codes for a particular protein and therefore a characteristic e.g tongue rolling
Genetic Variation
Differences in (DNA / genes / alleles), differences within a species
Genotype
The combination of alleles for each trait e.g BB, Bb or bb
Haploid
Cell with half the full complement of chromosomes (23 in humans)
Heterozygous
This means having a dominant and recessive allele e.g Bb
Homozygous
A pair of alleles that are the same e.g HH or hh
Hydrogen Bonds
Attractive forces that hold the two strands of DNA together
Inheritable
The information can be passed down on to the offspring. It must affect the genetic information in the gametes
Karyotype
A photograph or diagram of the chromosomes of a cell arranged in an orderly fashion
Meiosis
Cell division that reduces the number of chromosomes to half the normal number, producing 4 genetically different cells. This is what happens in the testes and ovary; meiosis produces gametes
Mitosis
This is a genetically exact division of a cell- produces 2 identical daughter cells
Mono hybrid Cross
A straightfoward cross involving only one pair of genes or alleles
Mutation
This is a sudden, permanent change in a gene or whole chromosome, a mutation is a change in the order of DNA bases that causes a new allele
Natural Selection
Organisms with characteristics best suited to their environment become more successful, and so expand in numbers
Non Inheritable
The information can be passed on to the offspring as it is due to a change in the somatic cells, due to environment. (Affects only the organism, not the offspring.)
Nucleotide
A unit built up of a base, a sugar and a phosphate group
Pedigree Chart
A family tree drawn with standard genetic symbols, showing inheritance patterns for specific characteristics e.g straight or curly hair
Phenotype Ratio
Ratio of phenotype’s e.g 3 brown hair : 1 blonde hair (a prediction of the phenotype’s and their occurrence as a result of a cross.)
Phenotype
The expression of a genotype; this is what you look like e.g brown or blue eyes
Phosphate
Group that alternates with the ribose sugar in the DNA backbone
Punnett Square
Name given to the grid of squares that may be drawn to show the range of combinations of genes that may occur
Pure Breeding
A group of identical individuals that always produce offspring of the same phenotype when interbred, they are homozygous individuals e.g BB or bb
Recessive
This is the allele which is only expressed if there are two such alleles e.g b
Reduction Division
Another name for meiosis
Ribose
A sugar group that alternates with the phosphate group in the DNA backbone
Semi Conservative
Each double stranded DNA molecule is composed of one parental strand and one newly male strand
Sexual Reproduction
Reproduction involving two parents, where the offspring has some features inherited from each
Somatic
Somatic cells are body cells
Symbols
Use of capital letter for the dominant gene and the same small letter for the recessive e.g R for round pea and r for wrinkled pea, where round (R) is dominant
Template
Pattern
Trait
Another word for characteristics e.g brown hair
Triplet Code
Genetic code made by sequences of three bases in the DNA e.g AAA, GCT, CAT etc
Variation
The differences among parents and their offspring or among individuals in a population
Zygote
Cell formed when a sperm cell fuses with an egg cell
